=Flexion Therapeutics (FLXN) : FDA approves Zilretta

The FDA  approved a knee pain treatment developed by Flexion Therapeutics, paving the way for the 10-year-old Burlington company to add around 100 sales jobs and begin generating sales revenue.

Analysts have estimated that Zilretta, a long-acting, non-opioid steroid injection for osteoarthritis of the knee, will eventually reap hundreds of millions of dollars in annual sales. It’s expected to compete with a similar treatment called Synvisc that is sold by French pharma giant Sanofi.

Since going public in 2014, Flexion (Nasdaq: FLXN) has grown from roughly a dozen employees to around 140. The company now plans to add around 100 field representatives to sell Zilretta, which is expected to be available in the U.S. by the end of October. (Job offers contingent on an FDA approval were extended prior to the decision.)

"We see Zilretta as the first step in what will be a long and fruitful journey," Flexion CEO Mike Clayman said in an interview. "We are ready to rock and roll."

Millions of Americans receive a steroid injection in the knee each year, but the pain relief typically wanes within a few weeks, and doctors advise against getting an injection more than once every three months. Zilretta, which combines a common corticosteroid with a polymer, is designed to make the pain relief last longer.

Flexion’s FDA application was based on a late-stage trial which showed patients who received Zilretta reported about half of the pain level, on average, of those on a placebo through 12 weeks.

Aside from Zilretta, Flexion is developing a longer-acting osteoarthritis drug that has yet to enter human trials. Clayman said that the company is also planning to acquire an external drug candidate.

"We expect (Zilretta) will make a real difference for patients and be a commercial success, generating resources that will allow us to fuel the pipeline," he said.